diff --git a/app/main.py b/app/main.py
index f112cc0..5f0ae45 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1,15 +1,25 @@
-from fastapi import FastAPI
+from fastapi import FastAPI, Request
+from fastapi.responses import HTMLResponse
+from fastapi.staticfiles import StaticFiles
+from fastapi.templating import Jinja2Templates
 from app.api.files import router as files_router
 from app.api.session import router as session_router
 from app.api.tvdb import router as tvdb_router
 
 app = FastAPI(title="Rename MVP")
+templates = Jinja2Templates(directory="app/templates")
 
 app.include_router(tvdb_router, prefix="/api/tvdb", tags=["tvdb"])
 app.include_router(session_router, prefix="/api/session", tags=["session"])
 app.include_router(files_router, prefix="/api/files", tags=["files"])
+app.mount("/static", StaticFiles(directory="app/static"), name="static")
 
 
 @app.get("/api/health")
 def health():
     return {"status": "ok"}
+
+
+@app.get("/", response_class=HTMLResponse)
+def index(request: Request):
+    return templates.TemplateResponse("index.html", {"request": request})
diff --git a/app/static/app.js b/app/static/app.js
new file mode 100644
index 0000000..96f3601
--- /dev/null
+++ b/app/static/app.js
@@ -0,0 +1,322 @@
+(function () {
+  const STORAGE_KEY = "rename_mvp_session_id";
+  const sessionId = initSessionId();
+  const state = {
+    sessionId,
+    selectedSeries: null,
+    episodes: [],
+    roots: [],
+    discoveredFiles: [],
+  };
+
+  const el = {
+    sessionMeta: document.getElementById("sessionMeta"),
+    outputBox: document.getElementById("outputBox"),
+    searchInput: document.getElementById("searchInput"),
+    searchBtn: document.getElementById("searchBtn"),
+    searchResults: document.getElementById("searchResults"),
+    seriesInfo: document.getElementById("seriesInfo"),
+    refreshEpisodesBtn: document.getElementById("refreshEpisodesBtn"),
+    episodesList: document.getElementById("episodesList"),
+    refreshSelectedEpisodesBtn: document.getElementById("refreshSelectedEpisodesBtn"),
+    clearSelectedEpisodesBtn: document.getElementById("clearSelectedEpisodesBtn"),
+    selectedEpisodesList: document.getElementById("selectedEpisodesList"),
+    rootsSelect: document.getElementById("rootsSelect"),
+    refreshRootsBtn: document.getElementById("refreshRootsBtn"),
+    subpathInput: document.getElementById("subpathInput"),
+    recursiveInput: document.getElementById("recursiveInput"),
+    discoverBtn: document.getElementById("discoverBtn"),
+    discoveredFilesList: document.getElementById("discoveredFilesList"),
+    refreshSelectedFilesBtn: document.getElementById("refreshSelectedFilesBtn"),
+    clearSelectedFilesBtn: document.getElementById("clearSelectedFilesBtn"),
+    selectedFilesList: document.getElementById("selectedFilesList"),
+    mappingPreviewBtn: document.getElementById("mappingPreviewBtn"),
+    filenamePreviewBtn: document.getElementById("filenamePreviewBtn"),
+    renameExecuteBtn: document.getElementById("renameExecuteBtn"),
+  };
+
+  function initSessionId() {
+    const existing = localStorage.getItem(STORAGE_KEY);
+    if (existing) return existing;
+    const created = "ui-" + Date.now() + "-" + Math.floor(Math.random() * 10000);
+    localStorage.setItem(STORAGE_KEY, created);
+    return created;
+  }
+
+  function q(path) {
+    return path.includes("?") ? `${path}&session_id=${encodeURIComponent(state.sessionId)}` : `${path}?session_id=${encodeURIComponent(state.sessionId)}`;
+  }
+
+  async function api(path, options = {}) {
+    const resp = await fetch(path, options);
+    const text = await resp.text();
+    let data = {};
+    try {
+      data = text ? JSON.parse(text) : {};
+    } catch (_err) {
+      data = { raw: text };
+    }
+    if (!resp.ok) {
+      throw new Error(data.detail || data.raw || `HTTP ${resp.status}`);
+    }
+    return data;
+  }
+
+  function out(label, payload) {
+    el.outputBox.textContent = `${label}\n${JSON.stringify(payload, null, 2)}`;
+  }
+
+  function makeActionButton(label, handler, secondary) {
+    const btn = document.createElement("button");
+    btn.textContent = label;
+    if (secondary) btn.className = "secondary";
+    btn.addEventListener("click", handler);
+    return btn;
+  }
+
+  function setLoading(btn, loading) {
+    if (!btn) return;
+    btn.disabled = loading;
+  }
+
+  async function loadRoots() {
+    const data = await api("/api/files/roots");
+    state.roots = data.items || [];
+    el.rootsSelect.innerHTML = "";
+    for (const root of state.roots) {
+      const opt = document.createElement("option");
+      opt.value = root.id;
+      opt.textContent = `${root.id}: ${root.path}`;
+      el.rootsSelect.appendChild(opt);
+    }
+    out("Roots loaded", data);
+  }
+
+  async function doSearch() {
+    const query = (el.searchInput.value || "").trim();
+    if (!query) return;
+    const data = await api(`/api/tvdb/search?q=${encodeURIComponent(query)}`);
+    el.searchResults.innerHTML = "";
+    (data.items || []).forEach((item) => {
+      const li = document.createElement("li");
+      const left = document.createElement("span");
+      left.textContent = item.display_name || item.name || "(no name)";
+      const right = document.createElement("div");
+      const btn = makeActionButton("Select", async () => {
+        state.selectedSeries = item;
+        el.seriesInfo.textContent = `Selected: ${item.display_name || item.name}`;
+        await loadEpisodes();
+      });
+      right.appendChild(btn);
+      li.appendChild(left);
+      li.appendChild(right);
+      el.searchResults.appendChild(li);
+    });
+    out("Search result", data);
+  }
+
+  async function loadEpisodes() {
+    if (!state.selectedSeries || !state.selectedSeries.id) {
+      throw new Error("Select a series first");
+    }
+    const data = await api(`/api/tvdb/series/${encodeURIComponent(state.selectedSeries.id)}/episodes?order_type=aired`);
+    state.episodes = data.items || [];
+    el.episodesList.innerHTML = "";
+
+    state.episodes.forEach((episode) => {
+      const li = document.createElement("li");
+      const left = document.createElement("span");
+      left.textContent = episode.label || `${episode.season_number}x${episode.episode_number} ${episode.title}`;
+      const right = document.createElement("div");
+      const btn = makeActionButton("Add", async () => {
+        const payload = {
+          id: episode.id,
+          series: state.selectedSeries.name,
+          year: state.selectedSeries.year,
+          season_number: episode.season_number,
+          episode_number: episode.episode_number,
+          title: episode.title,
+          aired: episode.aired,
+          label: episode.label,
+        };
+        const res = await api(q("/api/session/selected-episodes"), {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({ items: [payload] }),
+        });
+        await loadSelectedEpisodes();
+        out("Episode added", res);
+      });
+      right.appendChild(btn);
+      li.appendChild(left);
+      li.appendChild(right);
+      el.episodesList.appendChild(li);
+    });
+    out("Episodes loaded", data);
+  }
+
+  async function loadSelectedEpisodes() {
+    const data = await api(q("/api/session/selected-episodes"));
+    el.selectedEpisodesList.innerHTML = "";
+    (data.items || []).forEach((item, idx) => {
+      const li = document.createElement("li");
+      const left = document.createElement("span");
+      left.textContent = item.episode.label || item.episode.title || `Episode #${idx + 1}`;
+      const right = document.createElement("div");
+      right.appendChild(makeActionButton("Up", async () => {
+        if (idx === 0) return;
+        await api(q("/api/session/selected-episodes/reorder"), {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({ from_index: idx, to_index: idx - 1 }),
+        });
+        await loadSelectedEpisodes();
+      }, true));
+      right.appendChild(makeActionButton("Down", async () => {
+        if (idx >= data.items.length - 1) return;
+        await api(q("/api/session/selected-episodes/reorder"), {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({ from_index: idx, to_index: idx + 1 }),
+        });
+        await loadSelectedEpisodes();
+      }, true));
+      right.appendChild(makeActionButton("Remove", async () => {
+        await api(q(`/api/session/selected-episodes/${item.selection_id}`), { method: "DELETE" });
+        await loadSelectedEpisodes();
+      }, true));
+      li.appendChild(left);
+      li.appendChild(right);
+      el.selectedEpisodesList.appendChild(li);
+    });
+    return data;
+  }
+
+  async function discoverFiles() {
+    const rootId = el.rootsSelect.value;
+    if (!rootId) throw new Error("No root selected");
+    const subpath = encodeURIComponent((el.subpathInput.value || "").trim());
+    const recursive = el.recursiveInput.checked ? "true" : "false";
+    const data = await api(`/api/files/discover?root_id=${encodeURIComponent(rootId)}&subpath=${subpath}&recursive=${recursive}&limit=200`);
+    state.discoveredFiles = data.items || [];
+    el.discoveredFilesList.innerHTML = "";
+
+    state.discoveredFiles.forEach((file) => {
+      const li = document.createElement("li");
+      const left = document.createElement("span");
+      left.textContent = file.relative_path || file.name;
+      const right = document.createElement("div");
+      right.appendChild(makeActionButton("Add", async () => {
+        const payload = { path: file.path, name: file.name };
+        const res = await api(q("/api/session/selected-files"), {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({ items: [payload] }),
+        });
+        await loadSelectedFiles();
+        out("File added", res);
+      }));
+      li.appendChild(left);
+      li.appendChild(right);
+      el.discoveredFilesList.appendChild(li);
+    });
+    out("Discover result", data);
+  }
+
+  async function loadSelectedFiles() {
+    const data = await api(q("/api/session/selected-files"));
+    el.selectedFilesList.innerHTML = "";
+    (data.items || []).forEach((item, idx) => {
+      const li = document.createElement("li");
+      const left = document.createElement("span");
+      left.textContent = item.file.path || item.file.name || `File #${idx + 1}`;
+      const right = document.createElement("div");
+      right.appendChild(makeActionButton("Up", async () => {
+        if (idx === 0) return;
+        await api(q("/api/session/selected-files/reorder"), {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({ from_index: idx, to_index: idx - 1 }),
+        });
+        await loadSelectedFiles();
+      }, true));
+      right.appendChild(makeActionButton("Down", async () => {
+        if (idx >= data.items.length - 1) return;
+        await api(q("/api/session/selected-files/reorder"), {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({ from_index: idx, to_index: idx + 1 }),
+        });
+        await loadSelectedFiles();
+      }, true));
+      right.appendChild(makeActionButton("Remove", async () => {
+        await api(q(`/api/session/selected-files/${item.selection_id}`), { method: "DELETE" });
+        await loadSelectedFiles();
+      }, true));
+      li.appendChild(left);
+      li.appendChild(right);
+      el.selectedFilesList.appendChild(li);
+    });
+    return data;
+  }
+
+  async function callPreview(path, label) {
+    const data = await api(q(path));
+    out(label, data);
+  }
+
+  async function executeRename() {
+    const data = await api(q("/api/session/rename-execute") + "&confirm=true", {
+      method: "POST",
+    });
+    out("Rename execute", data);
+    await loadSelectedFiles();
+  }
+
+  async function withHandler(fn, btn) {
+    try {
+      setLoading(btn, true);
+      await fn();
+    } catch (err) {
+      out("Error", { detail: err.message || String(err) });
+    } finally {
+      setLoading(btn, false);
+    }
+  }
+
+  function bindEvents() {
+    el.searchBtn.addEventListener("click", () => withHandler(doSearch, el.searchBtn));
+    el.refreshEpisodesBtn.addEventListener("click", () => withHandler(loadEpisodes, el.refreshEpisodesBtn));
+    el.refreshSelectedEpisodesBtn.addEventListener("click", () => withHandler(loadSelectedEpisodes, el.refreshSelectedEpisodesBtn));
+    el.clearSelectedEpisodesBtn.addEventListener("click", () =>
+      withHandler(async () => {
+        const res = await api(q("/api/session/selected-episodes"), { method: "DELETE" });
+        await loadSelectedEpisodes();
+        out("Selected episodes cleared", res);
+      }, el.clearSelectedEpisodesBtn)
+    );
+    el.refreshRootsBtn.addEventListener("click", () => withHandler(loadRoots, el.refreshRootsBtn));
+    el.discoverBtn.addEventListener("click", () => withHandler(discoverFiles, el.discoverBtn));
+    el.refreshSelectedFilesBtn.addEventListener("click", () => withHandler(loadSelectedFiles, el.refreshSelectedFilesBtn));
+    el.clearSelectedFilesBtn.addEventListener("click", () =>
+      withHandler(async () => {
+        const res = await api(q("/api/session/selected-files"), { method: "DELETE" });
+        await loadSelectedFiles();
+        out("Selected files cleared", res);
+      }, el.clearSelectedFilesBtn)
+    );
+    el.mappingPreviewBtn.addEventListener("click", () => withHandler(() => callPreview("/api/session/mapping-preview", "Mapping preview"), el.mappingPreviewBtn));
+    el.filenamePreviewBtn.addEventListener("click", () => withHandler(() => callPreview("/api/session/filename-preview", "Filename preview"), el.filenamePreviewBtn));
+    el.renameExecuteBtn.addEventListener("click", () => withHandler(executeRename, el.renameExecuteBtn));
+  }
+
+  async function init() {
+    el.sessionMeta.textContent = `session_id: ${state.sessionId}`;
+    bindEvents();
+    await loadRoots();
+    await loadSelectedEpisodes();
+    await loadSelectedFiles();
+  }
+
+  init().catch((err) => out("Init error", { detail: err.message || String(err) }));
+})();
diff --git a/app/static/styles.css b/app/static/styles.css
new file mode 100644
index 0000000..704c82e
--- /dev/null
+++ b/app/static/styles.css
@@ -0,0 +1,138 @@
+* {
+  box-sizing: border-box;
+}
+
+body {
+  margin: 0;
+  padding: 0;
+  font-family: "Segoe UI", Tahoma, sans-serif;
+  background: #f2f4f8;
+  color: #1a1f2b;
+}
+
+.topbar {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  padding: 12px 16px;
+  background: #0f172a;
+  color: #e2e8f0;
+}
+
+.topbar h1 {
+  margin: 0;
+  font-size: 20px;
+}
+
+#sessionMeta {
+  font-size: 12px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: repeat(2, minmax(280px, 1fr));
+  gap: 12px;
+  padding: 12px;
+}
+
+.panel {
+  background: #ffffff;
+  border: 1px solid #d7dee9;
+  border-radius: 8px;
+  padding: 10px;
+}
+
+.panel h2 {
+  margin: 0 0 10px;
+  font-size: 16px;
+}
+
+.panel h3 {
+  margin: 10px 0 6px;
+  font-size: 14px;
+}
+
+.row {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  margin-bottom: 8px;
+}
+
+.stack {
+  display: flex;
+  flex-direction: column;
+}
+
+input[type="text"],
+select {
+  border: 1px solid #c3cedf;
+  border-radius: 6px;
+  padding: 6px 8px;
+  min-width: 160px;
+}
+
+button {
+  border: 1px solid #0f172a;
+  background: #0f172a;
+  color: #ffffff;
+  border-radius: 6px;
+  padding: 6px 10px;
+  cursor: pointer;
+}
+
+button.secondary {
+  background: #e2e8f0;
+  color: #1a1f2b;
+  border-color: #c3cedf;
+}
+
+.list {
+  list-style: none;
+  margin: 0;
+  padding: 0;
+  max-height: 260px;
+  overflow: auto;
+  border: 1px solid #e4eaf2;
+  border-radius: 6px;
+}
+
+.list li {
+  display: flex;
+  justify-content: space-between;
+  gap: 8px;
+  border-bottom: 1px solid #edf1f7;
+  padding: 6px 8px;
+  font-size: 13px;
+}
+
+.list li:last-child {
+  border-bottom: none;
+}
+
+.muted {
+  color: #475569;
+  font-size: 12px;
+  margin-bottom: 8px;
+}
+
+.output {
+  margin: 0 12px 12px;
+}
+
+#outputBox {
+  margin: 0;
+  background: #0b1220;
+  color: #dbeafe;
+  border-radius: 6px;
+  padding: 10px;
+  max-height: 320px;
+  overflow: auto;
+  font-size: 12px;
+}
+
+@media (max-width: 900px) {
+  .grid {
+    grid-template-columns: 1fr;
+  }
+}
diff --git a/app/templates/index.html b/app/templates/index.html
new file mode 100644
index 0000000..565511b
--- /dev/null
+++ b/app/templates/index.html
@@ -0,0 +1,87 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <title>Rename MVP</title>
+    <link rel="stylesheet" href="/static/styles.css" />
+  </head>
+  <body>
+    <header class="topbar">
+      <h1>Rename MVP</h1>
+      <div id="sessionMeta"></div>
+    </header>
+
+    <main class="grid">
+      <section class="panel" id="panelSearch">
+        <h2>Panel 1: TVDB Search</h2>
+        <div class="row">
+          <input id="searchInput" type="text" placeholder="Search series..." />
+          <button id="searchBtn">Search</button>
+        </div>
+        <div id="seriesInfo" class="muted"></div>
+        <ul id="searchResults" class="list"></ul>
+      </section>
+
+      <section class="panel" id="panelEpisodes">
+        <h2>Panel 2: Episodes</h2>
+        <div class="row">
+          <button id="refreshEpisodesBtn">Refresh Episodes</button>
+        </div>
+        <ul id="episodesList" class="list"></ul>
+      </section>
+
+      <section class="panel" id="panelSelectedEpisodes">
+        <h2>Panel 3: Selected Episodes</h2>
+        <div class="row">
+          <button id="refreshSelectedEpisodesBtn">Refresh</button>
+          <button id="clearSelectedEpisodesBtn">Clear</button>
+        </div>
+        <ul id="selectedEpisodesList" class="list"></ul>
+      </section>
+
+      <section class="panel" id="panelSelectedFiles">
+        <h2>Panel 4: Selected Files + File Discovery</h2>
+        <div class="stack">
+          <div class="row">
+            <label for="rootsSelect">Root</label>
+            <select id="rootsSelect"></select>
+            <button id="refreshRootsBtn">Refresh Roots</button>
+          </div>
+          <div class="row">
+            <input id="subpathInput" type="text" placeholder="Subpath (relative)" />
+            <label>
+              <input id="recursiveInput" type="checkbox" />
+              recursive
+            </label>
+            <button id="discoverBtn">Discover</button>
+          </div>
+          <div>
+            <h3>Discovered Files</h3>
+            <ul id="discoveredFilesList" class="list"></ul>
+          </div>
+          <div class="row">
+            <button id="refreshSelectedFilesBtn">Refresh Selected Files</button>
+            <button id="clearSelectedFilesBtn">Clear Selected Files</button>
+          </div>
+          <div>
+            <h3>Selected Files</h3>
+            <ul id="selectedFilesList" class="list"></ul>
+          </div>
+          <div class="row">
+            <button id="mappingPreviewBtn">Mapping Preview</button>
+            <button id="filenamePreviewBtn">Filename Preview</button>
+            <button id="renameExecuteBtn">Rename Execute (confirm=true)</button>
+          </div>
+        </div>
+      </section>
+    </main>
+
+    <section class="panel output">
+      <h2>Output</h2>
+      <pre id="outputBox"></pre>
+    </section>
+
+    <script src="/static/app.js"></script>
+  </body>
+</html>
diff --git a/data/session_state.sqlite3 b/data/session_state.sqlite3
index fa5c9b7..7b4364c 100644
Binary files a/data/session_state.sqlite3 and b/data/session_state.sqlite3 differ
diff --git a/feature_tests_ui.sh b/feature_tests_ui.sh
new file mode 100755
index 0000000..e3d480e
--- /dev/null
+++ b/feature_tests_ui.sh
@@ -0,0 +1,88 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+if [ -z "${BASE_URL:-}" ]; then
+  if curl --silent --fail http://127.0.0.1:8085/api/health >/dev/null 2>&1; then
+    BASE_URL="http://127.0.0.1:8085"
+  elif curl --silent --fail http://host.containers.internal:8085/api/health >/dev/null 2>&1; then
+    BASE_URL="http://host.containers.internal:8085"
+  else
+    echo "ERROR: could not determine BASE_URL. Tried 127.0.0.1 and host.containers.internal." >&2
+    exit 1
+  fi
+fi
+
+TMP_DIR="$(mktemp -d)"
+trap 'rm -rf "$TMP_DIR"' EXIT
+
+echo "== Feature test 1: root page renders 4 panels and action controls =="
+curl --fail --silent --show-error \
+  "${BASE_URL}/" \
+  -o "${TMP_DIR}/index.html"
+
+python3 - "${TMP_DIR}/index.html" <<'PY'
+import sys
+from pathlib import Path
+
+html = Path(sys.argv[1]).read_text(encoding="utf-8")
+required = [
+    "Panel 1: TVDB Search",
+    "Panel 2: Episodes",
+    "Panel 3: Selected Episodes",
+    "Panel 4: Selected Files + File Discovery",
+    "Mapping Preview",
+    "Filename Preview",
+    "Rename Execute (confirm=true)",
+]
+for needle in required:
+    assert needle in html, f"missing UI text: {needle}"
+print("UI panel/control validation passed")
+PY
+
+echo
+echo "== Feature test 2: static assets are served =="
+curl --fail --silent --show-error \
+  "${BASE_URL}/static/styles.css" \
+  -o "${TMP_DIR}/styles.css"
+curl --fail --silent --show-error \
+  "${BASE_URL}/static/app.js" \
+  -o "${TMP_DIR}/app.js"
+
+python3 - "${TMP_DIR}/styles.css" "${TMP_DIR}/app.js" <<'PY'
+import sys
+from pathlib import Path
+
+css = Path(sys.argv[1]).read_text(encoding="utf-8")
+js = Path(sys.argv[2]).read_text(encoding="utf-8")
+assert ".grid" in css, "styles.css missing expected grid styles"
+assert "session_id" in js, "app.js missing session_id usage"
+assert "/api/tvdb/search" in js, "app.js missing search endpoint usage"
+assert "/api/files/discover" in js, "app.js missing discovery endpoint usage"
+print("static assets validation passed")
+PY
+
+echo
+echo "== Feature test 3: UI references existing backend workflow endpoints =="
+python3 - "${TMP_DIR}/app.js" <<'PY'
+import sys
+from pathlib import Path
+
+js = Path(sys.argv[1]).read_text(encoding="utf-8")
+required_endpoints = [
+    "/api/tvdb/search",
+    "/api/tvdb/series/",
+    "/api/session/selected-episodes",
+    "/api/session/selected-files",
+    "/api/files/roots",
+    "/api/files/discover",
+    "/api/session/mapping-preview",
+    "/api/session/filename-preview",
+    "/api/session/rename-execute",
+]
+for endpoint in required_endpoints:
+    assert endpoint in js, f"missing endpoint usage in UI: {endpoint}"
+print("endpoint wiring validation passed")
+PY
+
+echo
+echo "All UI feature tests passed."